JBSTRD

I have been trying to figure out a high idle issue on my 2000 4Runner (3.4L) for a couple of months.

The original problem-

Initially, when I would start the engine, the idle was high to begin with (~1500 rpm's) as is normal when the engine is cold. When the engine would warm up, the idle would never drop below ~1000-1050 rpm's. Another wierd thing was when I would push the clutch in or take it out of gear completely, the idle would stay high. As I was rolling faster than about 10-15 mph, the idle would stay at around 1500-1600 rpm's, but as soon as the vehicle got under 10-15mph, the idle would then drop down to the 1000-1050 rpm's.

To make things more confusing, the engine would randomly go back down to the normal idle of ~700. I could not pinpoint any specific time it would do this, hence the reason I say random.

Possible fixes-

I did a lot of reading on various sites in an attempt to self diagnose the problem. I found that a lot of people had similar issues. Most people tend to have issues with their Idle Air Control (IAC) Valve. They recommend taking it off and cleaning it out. I have heard mention of Coolant Temp Sensors causing idle issues or Throttle Position Sensors being bad.

So, I decided to take the Throttle Body and IAC Valve off to clean them. I ordered a new Throttle Body Gasket and a new IAC Valve Gasket. I took the Throttle Body off and separated the IAC Valve. There was a decent amount of carbon buildup in it, but I cleaned it all out. I took off the light green magnet portion of the IAC Valve so I could open/close the valve to clean it better. There are two screws that have been sealed with silicon, so I re-sealed them when I put the magnet back on. I made sure to put a small enough bead that it would not get into the valve or interfere with the magnet. While everything was apart, I checked all vacuum hoses and cleaned the MAF Sensor. I re-installed everything with the new gaskets in place.

New Problem-

When I started the 4Runner up, the idle seemed slightly lower than the previous cold engine idle was. It was now idling at about 1200 rpm's. However, when the engine warmed up and I started driving it, the idle would stay between 1400-1500 rpm's. Another new issue is when I am in neutral or the clutch is in and I am coasting to a stop, the engine revs from ~1000 to ~1500 if I am over 10-15mph. It is a consistent vrooom, vrooom, vrooom, until I drop below 10-15 mph. Then, it will raise to ~1400-1500 rpm's and stay that way.

I read that sometimes the ECU needs to re-learn the idle speed after you clean out the Thottle Body/IAC Valve, but I have driven it about 150 miles and it is not going back to normal.

I am at a loss. Does this issue sound familiar to anybody? Any suggestions? I do not want to start buying parts I do not need. I am curious as to why the idle issue changed after I cleaned out the IAC Valve. I have not had any engine codes either.

Thanks for enduring this long post. Any help is appreciated.

JBSTRD

I believe I have fixed my idle issue. I took the IAC back off and re-checked it. It functioned perfectly fine. However, despite the fact I replaced the gasket with a new Toyota one, it appeared it was not sealing all the way with just the gasket. It looked like there was a small amount of coolant spilling into the other chambers of the IAC. I re-sealed it with the gasket and RTV together. I let it dry and was amazed when I started it up and it idled down to 750.

I am so happy I have my normal idle back!!!